Purification of rock minerals



Patented Jan. 2, 1940 UNITED STATES PURIFICATION OF ROCK MINERALS Oliver0. Ralston, Hyattsville, Md., assignor to Government of the UnitedStates, as represented by the Secretary of the Interior No Drawing.Application April 9, 1938, Serial No. 201,203

6 Claims.

(Granted under the act of March 3; 1883, as

amended April 30, 1928; 370 0. G. 757) in the non-metallic minerals ofthe type found all in Florida, Tennessee, Idaho and Montana.

During the early part of the 20th century the phosphate deposits,particularly those of Florida, were worked and processed, first bymerely crushing the ore and later by methods in which the phosphateswere extracted from the ore. As late as the last decade this method ofconcentrating the valuable mineral away from the residue became highlydeveloped by processes variously referred to as froth flotation, filmflotation, loose agglomeration on wet stratifying tables, certain ofwhich are described by OMeara, R. G., in a report of investigation No.3139, Bureau of Mines, 1931, entitled "Added recovery by hydraulicsizing of fine material in the land-pebble district of Florida and byOMeara, R. G. and Pamplin, J. W., in a report of investigation No. 3195,Bureau of Mines, 1932, entitled Selective oiling and table concentrationof phosphatic sands in the land-pebble district of Florida. Theseprocesses may be briefly described as consisting of:

Wet screening the ore at about 20 mesh to recover the plus 20-meshmaterial, the finer material going to waste, or further separated byhydraulic classifiers. The material is agitated for a short period with4 to 5 lbs, of previously emulsified fuel oil (21 to 22 B.) and 1 /2 to2 lbs. of sodium oleate per ton, the phosphate grains alone taking upthe oil and becoming agglomerated. This aggiomerate is then treated bytabling to recover the high grade concentrate.

From experience it has been found that any reagent used in the processof refining phosphate ores which costs more than one tenth the marketprice of the concentrated phosphate mineral renders such processimpracticable since at its best the market for highest grade (70-80% B.P. L.) refined phosphate ore was between 3.50 to $4.00 per ton and theprevailing price is around $2.50 per ton.

In these prior methods in which the valuable ore is floated from thegangue residue, filming of the phosphate has been accomplished by use offatty acids, fatty acid sodium salts (soaps) and related agents in whichthe active constituent was the anion and for this reason have beenreferred to as anionic agents. These anionic agents film or adhere tothe phosphates in preference to filming or adhering to the silica andsilicates of the ore. This film on the phosphates is easily augmented byand can be enhanced in thickness and water repellence by adding oils ofcheaper costs if desired, 'such as vegetable, animal or mineral oils.

To reduce the amount of filming agents depressing salts such as waterglass have been added to the ground ore pulp.

However, I have found that the presence of iron and aluminum saltsminimizes the selective characteristic of these anionic agents for thereason that they activate the silica and silicate minerals and are notdesired in soap flotation or table agglomeration.

Furthermore, I have found that with the phosphate ores the phosphate isspongy and of high surficial area in comparison with smooth surfaces-oflow surficial area of the compact silica minerals. Accordingly a muchlarger amount of filming agent is required than if the silica andsilicate minerals were filmed and floated.

I have also found that in agglomerate tabling there is a distinctadvantage in removing the major mineral by filming and agglomeration andhave discovered a process of concentrating the gangue away from the oreinstead of concentrating the valuable mineral.

In this process I make use of cationic agents (so named because, incontrast to the soaps, the active agent is in the cation or positive ionof the compound) which film quartz, clay, silicates and aluminosilicates and the other acidic minerals in preference to some of themore basic minerals such as the phosphates. These cationic agents areparticularly adaptable to the separation of quartz, clay, silicates andalumina-silicates from phosphates because of the presence of iron andaluminum salts in the ores.

Although the iron and aluminum salts in the phosphate ores are inrelatively non-ionized state so that their activating effect is small, Ihave found that because of the preponderance of the silica and silicateminerals in the Florida ores the addition of one to two pounds of thesesalts per ton to the ore pulp, the amount of filming reagent is"appreciably reduced since the cost of these activators is practicallynegligible in comparison with the cost of the filming agents.

. In concentrating phosphate ores as much clay aspossible should beremoved before attempting any filming method of concentration, becausethe clay is very absorbent and is a thief of filming, reagents. Washingout the clay. is already common practice but the washing also removesfinely divided phosphate. One aspect of my invention is partial orcomplete removal of clay for clay removal without losing finely dividedphosphate are compounds of the short-chain amino type, like diamyl amineor triethanol amine. in which no substitute of over five carbon atoms ispresent; or reagents of the simpler nitrogenous bases like pyridine orits related homologues and derivatives like quinoline (where a pyridinering has four extra carbon atoms in a side substituent) Cationicreagents with substituents that are too long are too strongly adsorbedon clay and will be required in greater amounts as the length of thecarbon chains increases. Therefore, compounds whose substituents containnot over five carbon atoms are best adapted to clay removal by filmingmethods. From one-half pound to five pounds of reagent per ton solidstreated is sufficient.

The resulting tailing from this clay removing operation may then beconcentrated by filming methods to separate the quartz and othersilicates from the phosphate. For this separation cationic reagentscontaining substituted ammonium ions are used, in which the substituentsare groups with over twelve carbon atoms, such as mono-lauryl amine,di-lauryl amine, tri-lauryl amine, tetra-lauryl ammonium hydroxide, orthe corresponding cetyl, stearyl, or oleyl bases or the simple salts ofthese bases. Less than two pounds of these compounds per ton of feedwill suffice if the clay has been well removed by the use of theshort-chain amines or ammonium salts. The poorer the colloidal clayremoval of the first step,

- the higher the reagent consumption in this secnd step. Betteradherence of these reagents to quartz and silicates is secured if metalion activators like iron or aluminum ions or their anologues, to theextent of one or two pounds per ton ore, are used. To further enhancegreasiness or waterrepe1lence of the film on the mineral, any easilyfiuid hydrocarbon oil can also be added to the pulp during mixing. Fromone to ten pounds per ton. solids will suffice. This addition isoptional but tends to permit economy in use of cationic reagent. Thereagents suitable ior clay removal are not efilcacious for filmingquartz or feldspathic minerals. The films they produce are notsufficiently greasy in character to permit good water-repellence fromthe glassy quartz or silicate surfaces. Reagents with substituentsintermediate between five and twelve carbon atoms are more stronglyadsorbed on clay minerals, so that increasing amounts of them areneeded, but not sufilciently eificient for filming the quartz andsilicate minerals.

In my process of filming and separating siliceous minerals the readilyavailable substituted ammonium compounds from the simple amines to thequaternary ammonium salts function particularly well when theconfiguration and magnitude of the substituents for the hydrogen of theammonia or ammonium radical are selected with respect to the particularmineral to be filmed.

Examples of these cationic agents which I have used with success are thediethanol and triethanol amines. Diamyl-amine and the amines of longerchain substituents, especially those with eight or more carbon atoms inthe chain have proven especially useful. Quaternary salts which are welladapted for use in this process In my process ass-distinguished from theprior processes as applied to low grade phosphates the minor mineral isthe one which remains in the riflies of the agitating table and travelsalong their length and over the end. The major mineral is filmed andagglomerated and immediately rafted over the side of the table throughthe shortest path.

Since ores from the Sangully mine in Florida consist primarily of clay,silica, and phosphate,

the feldspars and mica having weathered into the clay, so that they areremoved 'by the desliming process, the application of my process to orefrom this mine will serve to illustrate my invention.

A sample of the quartz-phosphate sands of this mine containing about 29%phosphate was deslimed by the process above described and the wettedthick sand pulp filmed by the addition of 0.44 pound trl-methyl-stearylammonium bromide accompanied by 3.6 pounds crude oil per ton solids.This was separated on a Wilfley table, the filmed and agglomeratedquartz being rafted over the side of the table and referred tohereinafter as the concentrate, with retreatment of tailing to give ascavenger concentrate which was added to the first concentrate with thefollowing results as determined by grain count:

' Phos- Weight PM Percent Combined concentrate (quartz) 127 2. 2 Telling(phosphate) 98 75. 0

amine or tri-ethanol-amine with non-saponifiable oils and froth floatedthe filmed clay and then filmed the quartz and feldspar with aquaternary ammonium hydroxide or salt with at least one substituentradical of the long chain type like tri-methyl-cetyl ammonium iodide.Alternatively, I have filmed the aluminosilicates such as the micas andfeldspars with salts of a single long substituent primary amine such asthe hydrochloride or primary lauryl amine. While I have found that theuse of non-saponifiable oil in froth flotation leads to economy in theuse of the cationic agents, it is not so necessary as in the agglomerateseparation process and may be omitted if desired without departing fromthe spirit of my invention.

From the foregoing it is apparent that detail changes may be made toadapt my process to ores of different composition without departing fromthe spirit of my invention as defined in the claims appended hereto andit is to be understood that the foregoing description is merelyillustrative of my invention without limitation to the specificcompounds mentioned therein.

Having thus described my invention, what I claim is:

1. The process of concentrating phosphate bearing minerals whichconsists in agitating a pulp of the ore containing the phosphate bearingmineral with two to fivepounds per ton of a cationic compound of shortchain amino type with substituents containing from two to five carbonatoms whereby the clay is made water repellent, treating the pulp withan aqueous separation process to remove the filmed clay, agitattrate andcollecting the tailing as a relativelyrich phosphate.

2. The process of concentrating phosphate bearing minerals whichconsists in agitating a pulp of the ore containing the phosphate bearingmineral with two to five pounds per ton of a cationic compound of shortchain amino type with substituents containing two to five carbon atomswhereby the clay is made water repellent, treating the pulp with anaqueous separation process to remove the filmed clay, agitating the'tailing resulting with a mineral oil and a cationic substituted ammoniumcompound with one to four substituents carrying over twelve carbon atomsin an amount less than 2 pounds per ton of ore, and separating from thepulp a material relatively rich in siliceous gangue and relatively poorin phosphate as a concentrate and collecting the tailing as a relativelyrich phosphate.

3. The process of concentrating phosphate bearing minerals whichconsists in agitating a pulp of the ore containing the phosphate bearingmineral with a cationic compound of short chain amino type withsubstituents containing two to five carbon atoms and a mineral oilwhereby the clay is made water repellent, treating the pulp with anaqueous separation process to remove the filmed clay, agitating theresulting tailing with a cationic substituted ammonium compound with oneto four organic radicals carrying over 5 carbon atoms in an amount lessthan 6 pounds per ton of ore, and separating from the pulp a materialrelatively rich in siliceous gangue and relatively poor in phosphatevalues as a concentrate and collecting the tailing as a relatively richphosphate.

4. In a process of concentrating phosphate ores the step of filming theclay in the absence of activators with two to five pounds per ton of oreof a cationic compound of the short chain amino type with substituentscontaining not over five carbon atoms.

5. In the process 01 concentrating phosphate k ores the step of filmingthe clay with a cationic short chain nitrogeneous aromatic base withsubstituents containing from 2 to 5 carbon atoms in an amount less thanfive pounds per ton of ore.

6. The process of concentrating phosphate bearing minerals whichconsists in agitating the pulp or the ore containing the phosphatebearing mineral with mineral oil, a cationic substituted ammoniumcompound with one to tour organic radicals carrying over 5 carbon atoms,and an activating agent of the iron and aluminum class causing thesiliceous gangue to have a surficial amnity for the substituted ammoniumcompound, separating trom the pulp a material relatively rich insiliceous gangue and relatively poor in phosphate values as aconcentrate and collecting the tailing as a relatively rich phosphate.

OLIVER C. RALSTON.

